A vehicle can include an internal combustion engine coupled to a transmission and a final drive to rotate wheels that move the vehicle. To start the engine of a non-hybrid vehicle, a starter motor can be energized which causes a crankshaft of the engine to turn and start the engine.
A hybrid electric vehicle utilizes both an electric motor-generator and an internal combustion engine to offer reduced fuel consumption and emissions. One type of hybrid electric vehicle utilizes a belted-alternator-starter (BAS). The BAS utilizes a motor-generator coupled to a crankshaft of the engine usually by a belt and pulley system. The motor-generator can restart the engine when a brake is released at a stop light and the motor-generator can be rotated by the engine during regenerative braking. This type of hybrid vehicle utilizes a starter motor independent of the motor-generator to start the engine when the engine has been shut off for an extended period of time. The starter motor and the motor-generator operate separately, i.e., not coupleable to each other.
Another hybrid electric vehicle utilizes a motor-generator coupled to a crankshaft of the internal combustion engine by a planetary gear and clutch system. The crankshaft rotates about an axis and the motor-generator is disposed coaxial with the axis. The planetary gear and clutch system includes a planetary gear set disposed coaxial with the axis and is incorporated into the motor-generator to start the engine when the engine has been shut off for an extended period of time.
Yet another hybrid electric vehicle utilizes a motor-generator coupled to a crankshaft of the internal combustion engine by a belt and pulley system. The system includes a crankshaft pulley coupled to the crankshaft and a motor-generator pulley coupled to a shaft of the motor-generator, with a belt disposed about the pulleys to transfer torque between the crankshaft and the shaft of the motor-generator. The system can further include a planetary gear set and a pair of clutches, with the planetary gear set and clutches either coupled to the crankshaft pulley of the crankshaft or coupled to the shaft of the motor-generator. The crankshaft and the crankshaft pulley are rotatable about a first axis and the shaft of the motor-generator and the motor-generator pulley are rotatable about a second axis spaced from the first axis. Generally, actuation of either of the clutches couples the crankshaft and the shaft of the motor-generator together through the belt. When the planetary gear set and the clutches are coupled to the crankshaft pulley, the planetary gear set and the clutches are coaxial with the first axis of the crankshaft pulley, and when the planetary gear set and the clutches are coupled to the shaft of the motor-generator, the planetary gear set and the clutches are coaxial with the second axis of the shaft of the motor-generator. One clutch operates to rotatably couple the crankshaft and the shaft of the motor-generator together through the belt at a ratio relative to the sizes of the crankshaft pulley and the motor-generator pulley. The other clutch operates to rotatably couple the crankshaft and the shaft of the motor-generator together though both the belt and the planetary gear set, at a ratio relative to the sizes of the crankshaft pulley and the motor-generator pulley, as well as the ratio through the planetary gear set, i.e., these ratios are multiplied together. Therefore, all torque flows through the belt in this belt and pulley system. This type of hybrid vehicle can either start the engine utilizing only the belt and pulley system or utilizing a starter motor independent of the motor-generator. When utilizing the separate starter motor, the starter motor and the motor-generator operate separately, i.e., not coupleable to each other.